~ Musings on weather and science

Slow Cooling Ahead…And How Can You Get Frost With Above Freezing Temperatures?

While we may start to feel temperatures drop and see some cloudiness in the latter half of the week, it doesn’t look like there’s much chance of getting any rainfall out of the deal. A low pressure center which is now off the British Columbia coastline will very slowly drop to the southeast nudging the high pressure ridge over the Great basin a bit each day off to the east. Temperatures will slowly fall from the mid-90s on Tuesday to the upper 80s by Thursday before dropping to the mid-80s by the end of the weekend. The low itself probably won’t get quite close enough to bring us any precipitation, but we could see varying amou8nts of cloudiness through the end of the week.

It was refreshing to get the following e-mail: “I live about 90 miles north of Elko and not too far from Wildhorse Reservoir. The last few mornings the temperature has been 36º to 38º. Yet when I go out before sunrise there is light frost on the grass and ice has formed on the car. Do you have an explanation for this?”

I do, but before I answer, I must assume that this only occurs on a clear night. Why on a clear night? Because of radiational cooling. I’ll explain tomorrow.